Antenna apparatus

ABSTRACT

This invention provides an antenna apparatus ( 60 ) for use in a non-contact type IC card into and from which data can be written and read by electronic apparatuses having a communication function, by virtue of inductive coupling. The antenna apparatus comprises a loop coil ( 61 ) and a magnetic member ( 62 ). The loop coil is produced by winding a conductive wire in a plane and configured to perform the inductive coupling. The magnetic member covers one region ( 61   a ) of the loop coil, provided at one side, from one surface of the loop coil, passes through the loop coil, and covers the other region ( 61   b ) of the loop coil, provided at the other side, from the other surface of the loop coil. The entire region of the loop coil is thus covered.

TECHNICAL FIELD

The present invention relates to an antenna apparatus for use innon-contact type IC cards into and from which data can be written andread when the cards are induction coupled with an electromagnetic fieldby electronic apparatuses having a communication function.

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 2005-192561, filed in Japanon Jun. 30, 2005, the entire content of which is incorporated herein byreference.

BACKGROUND ART

In recent years, so-called radio frequency Identification (RFID) systemsthat use non-contact type IC cards or IC tags have been introduced intoautomatic gates at railway stations, entrance/exit security systems,electronic money systems, and the like. As FIG. 1 schematically shows,the RFID system comprises a non-contact type IC card 100 and areader/writer 101. The reader/writer 101 can write data into, and readdata from, the IC card 100. In the RF system, when a loop antenna 102provided on the reader-writer 101 radiates a magnetic flux, the magneticflux is magnetically coupled with a loop antenna 103 provided on the ICcard 100, in accordance with the principle of electromagnetic induction.Thus, communication is performed between the IC card 100 and thereader/writer 101.

In the RFID system, the user need not insert the IC card into thereader/writer or set the IC card into contact with the metal contactpoint provided on the reader/writer as is required in the conventionalcontact-type IC card system, and data can be easily and fast written andread into and from the IC card. Since the reader/writer 101 suppliespower to the IC card 100 by virtue of electromagnetic induction, the ICcard 100 need not incorporate a power supply such as a battery. The RFIDsystem therefore can provide IC cards that are simple in configurationand, inexpensive and reliable.

However, the IC card may fail to communicate with the reader/writer ifit incorporates an IC tag having communication frequency of 13.56 MHz.That is, the IC tag is influenced by any metal member that lies near theIC card. In the communication achieved at 13.56 MHz by virtue ofelectromagnetic induction, the IC tag is influenced by any metal memberthat exists near it, inevitably changing inductance. The change ininductance results in a shift of the resonance frequency or a change inthe magnetic flux. As a result, no power can be attained.

In the RFID system described above, to ensure he communicable rangebetween the IC card 100 and the reader/writer 101, the IC card 100 needsto have the loop antenna 103 that can emit an electromagnetic fieldhaving a sufficient magnetic field intensity.

A technique that can reduce the influence a metal housing imposes on theloop antenna is known, other than the technique of arranging the loopantenna in an open space. Jpn. Pat. Appln. Laid-Open Publication No.2001-331772, for example, discloses an antenna apparatus for use in ICcards. This antenna apparatus has a plate of magnetic material, whichreduces the influence of any metal member.

DISCLOSURE OF INVENTION Object the Invention is to Achieve

With an antenna apparatus of the type described in the above patentpublication, the communication distance can be increased, but to someextent only. Since the communication range is narrow, communicationerrors may occur with the non-contact type IC card in some cases.Consequently, the non-contact type IC card cannot fully achieve itsconvenience.

Accordingly, a technical object of the present invention is to providean antenna apparatus for use in non-contact type IC card, which can notonly be small and thin, but also increase the communication distancebetween the IC card and an electronic apparatus with a communicationfunction.

An antenna apparatus, which is an embodiment of this invention, isdesigned for use in a non-contact type IC card into and from which datacan be written and read by electronic apparatuses having a communicationfunction, by virtue of inductive coupling. The antenna apparatuscomprises: a loop coil produced by winding a conductive wire in a planeand configured to perform the inductive coupling; and a magnetic membercovering one region of the loop coil, provided at one side thereof, fromone surface of the loop coil, passing through the loop coil, andcovering another region of the loop coil, provided at the other sidethereof, from the other surface of the loop coil. The magnetic membercovers the loop coil at the one surface and from the other surface, andthe entire region of loop coil is therefore covered.

The antenna apparatus can be small and thin, can yet increase thecommunication distance with respect to the electronic apparatus having acommunication function and can therefore expand the communication range.

Other objects of the invention and the advantages the invention achieveswill become apparent from the embodiments that will be described belowwith reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing a conventional RFID system;

FIG. 2 is a circuit diagram showing an RFID system that uses an antennaapparatus according to the present invention;

FIG. 3 is a plan view showing the antenna apparatus according to thisinvention;

FIG. 4 is a side view depicting the distribution of a magnetic field atthe antenna apparatus according to this invention;

FIG. 5 is a sectional view taken along line A-A shown in FIG. 3;

FIG. 6 is a plan view of an antenna apparatus according to anotherembodiment of the present invention;

FIG. 7 is a plan view of an antenna apparatus, which is comparativeexample 1 for comparison with the antenna apparatus according to thisinvention;

FIG. 8 is a side view of the antenna apparatus, or comparative example1;

FIG. 9 is a plan view of an antenna apparatus, which is comparativeexample 2 for comparison with the antenna apparatus according to thisinvention;

FIG. 10 is a side view of the antenna apparatus, or comparative example2;

FIG. 11 is a plan view of an antenna apparatus, which is comparativeexample 3 for comparison with the antenna apparatus according to thisinvention;

FIG. 12 is a side view of the antenna apparatus, or comparative example3;

FIG. 13 is a plan view of an antenna apparatus, which is comparativeexample 4 for comparison with the antenna apparatus according to thisinvention; and

FIG. 14 is a side view of the antenna apparatus, or comparative example4.

BEST MODE FOR CARRYING OUT THE INVENTION

Antenna apparatuses according to the embodiment of the present inventionwill be described with reference to the drawings appended hereto.

First, an RFID system using an antenna apparatus according to thisembodiment will be explained. As shown in FIG. 2, the RFID systemcomprises a non-contact type IC card 1 and a reader/writer 50(hereinafter referred to as R/W). The R/W 50 can write data into, andread data from, the IC card 1.

The IC card 1 is a battery-less IC card that does not incorporate apower supply such as a battery, in compliant with, for example, ISO7810Standard. The IC card 1 is of the same size as a so-called credit card.That is, it is rectangular and has such short sides and long sides thatit can be placed, in its entirety, on the palm of the hand. The IC card1 incorporates a substrate and has a loop antenna 2 and an integratedcircuit (IC) 3. The loop antenna 2 and the IC 3 are mounted on thesubstrate. The loop antenna 2 receives and transmits data when it iscoupled with an electromagnetic field. The IC 3 includes electroniccircuits and a memory. The electronic circuits perform variousprocesses.

The loop antenna 2 is constituted by a loop coil 4 formed by winding aconductive wire in a plane. The loop coil 4 is connected in parallel toa capacitor 5. The coil 4 and the capacitor 5 constitute a resonancecircuit. The loop antenna 2 is coupled with the electromagnetic fieldradiated from the loop antenna provided on the R/W 50, which will bedescribed later. The loop antenna 2 converts the electromagnetic fieldinto an electric signal, which is supplied to the IC.

The IC 3 comprises a rectifier circuit 6, a regulator 7, a high-passfilter (HPF) 8, a demodulation circuit 9, a sequencer 10, a memory 11,and a modulation circuit 12. The rectifier circuit 6 receives theelectric signal supplied from the loop coil 4 and rectifies the signal,smoothing the same. The regulator 7 receives the electric signalsupplied from the rectifier circuit 6 and converts the signal to ACpower. The HPF 8 extracts a high-frequency component from the electricsignal supplied from the rectifier circuit 6. The demodulation circuit 9demodulates the high-frequency signal input from the HPF 8. Thesequencer 10 controls the data-writing process and data-reading processin accordance with the data supplied from the demodulation circuit 9.The memory 11 stores the data supplied from the demodulation circuit 9.The modulation circuit 12 modulates the data transmitted from the loopcoil 4.

The rectifier circuit 6 comprises a diode 13, a resistor 14 and acapacitor 15. The anode terminal of the diode 13 is connected to one endof the loop coil 4 and to one end of the capacitor 5. The cathodeterminal of the diode 13 is connected the other end of the resistor 14and the other end of the capacitor 15. The resistor 14 and the capacitor15 are connected, at the other end, to the other end of the loop coil 4and the other end of the capacitor 5. The rectifier circuit 6 outputs anelectric signal generated by rectifying and smoothing the electricsignal supplied from the loop coil 4. The signal output from therectifier circuit 6 is supplied to the regulator 7 and the HPF 8.

The regulator 7 is connected to the cathode terminal of the diode 13, toone end of the resistor 14 and to one end of the capacitor 15 of theabove-described rectifier circuit 6. The regulator 7 controls thevoltage fluctuation (data component) of tins electric signal suppliedfrom the rectifier circuit 6, thereby stabilizing this electric signal.The signal thus stabilized is supplied, as DC power, to the sequencer10. Thus, the voltage fluctuation that occurs as the IC card 1, forexample, moves and the voltage fluctuation that occurs as the powerconsumed in the IC card 1 changes, are suppressed. Note that suchvoltage fluctuations may cause the sequencer 10 to make errors in itsoperation.

The HPF 8 comprises a capacitor 16 and a resistor 17. It extracts thehigh-frequency component from the electric signal supplied from therectifier circuit 6. The high-frequency component is supplied to thedemodulation circuit 9.

The demodulation circuit 9 is connected to the other end of thecapacitor 16 and one end of the resistor 17 of the above-described HPF8. It demodulates the high-frequency signal input from the HPF 8 andoutputs the signal to the sequencer 10.

The sequencer 10 incorporates a read only memory (ROM) and a randomaccess memory (RAM) and is connected to the demodulation circuit 9. Inthe sequencer 10, the signal (command) input from the demodulationcircuit 9 is stored into the RAM and is analyzed in accordance with tireprogram stored in the ROM. On the basis of the results of analysis, thedata stored in the memory 11 is read as needed, or the data suppliedfrom the demodulation circuit 9 is written into the memory 11. Thesequencer 10 generates a response signal, which is supplied to themodulation circuit 12, giving a response to the command.

The memory 11 is constituted by a nonvolatile memory such as anelectrically erasable programmable read-only memory (EEPROM) and isconnected to the sequencer 10 described above. The memory 11 stores thedata supplied from the demodulation circuit 9 on the basis of theresults of the analysis performed by the sequencer 10.

The modulation circuit 12 is constituted by a serial circuit ofimpedance 18 and a field-effect transistor (FET) 19. The impedance 18 isconnected, at one end, to the cathode terminal of the diode 13 providedin the rectifier circuit 6, and at the other end, to the drain terminalof the FET 19. The source terminal of the FET 19 is connected to theground. The gate terminal of the FET 19 is connected to the sequencer10. The modulation circuit 12 is connected in parallel to the loop coil4 that constitutes the above-mentioned resonance circuit. The modulationcircuit 12 causes the FET 19 to perform switching in accordance with thesignal supplied from the sequencer 10. Namely, the modulation circuit 12performs so-called added modulation, causing fluctuation of the load ofthe impedance 18, with respect to the loop coil 4.

On the other hand, the R/W 50 comprises a control circuit 51, amodulation circuit 52, a demodulation circuit 53, and a loop antenna 54.The control circuit 51 controls the data to be transmitted and received.The modulation circuit 52 modulates data, and the demodulation circuit53 demodulates data. The loop antenna 54 transmits and receives datawhen coupled with an electromagnetic field.

The control circuit 51 generates control signals in accordance with theinstructions externally input or the program stored. The control signalscontrol the modulation circuit 52 and the demodulation circuit 53 andgenerate transmission data that corresponds to the instructions. Thetransmission data is supplied to the modulation circuit 52. Further, thecontrol circuit 51 reproduces data from the response data supplied fromthe demodulation circuit 53. The data thus reproduced is output to anexternal apparatus.

The modulation circuit 52 modulates the transmission data input from thecontrol circuit 51. The data modulated is supplied to the loop antenna54.

The demodulation circuit 53 demodulates a modulated wave supplied fromthe loop antenna 54, generating demodulated data. This data is suppliedto the control circuit 51.

The loop antenna 54 is constituted by a loop coil formed by winding aconductive wire in a plane. The antenna 54 radiates an electromagneticfield that corresponds to the modulated wave supplied from themodulating circuit 52. The antenna 54 also detects the load fluctuationof the loop coil 4. A capacitor for resonance may be connected inparallel or in series to the loop antenna 54, in accordance with thedrive-circuit system of the R/W 50.

In the RFID system so configured as described above, when a data-writeinstruction is given to the IC card 1 the control circuit 51 of the R/W50 generates a write command signal in accordance with the instruction.At the same time, the control circuit 51 generates transmission data(data to be written) that accords with the data-write instruction. Thetransmission data is supplied to the modulation circuit 52. Themodulation circuit 52 then modulates the amplitude of the oscillationsignal. The signal thus modulated is supplied to the loop antenna 54.The loop antenna 54 radiates an electromagnetic signal corresponding tothe modulated signal input to the R/W 50.

The resonance circuit provided in the IC card 1 and constituted by theloop coil 4 and the capacitor 5 has a resonance frequency of, forexample, 13.56 MHz. This frequency corresponds to the oscillationfrequency (carrier frequency) of the signal transmitted from the R/W 50.Hence, the resonance circuit performs resonance, receiving theelectromagnetic field radiated from the loop antenna 54. The resonancecircuit converts the electromagnetic field into an electric signal,which is then supplied to the IC 3. In the IC 3, the electric signal isinput to the rectifier circuit 6. The rectifier circuit 6 rectifies thesignal, smoothing the same. The electric signal thus smoothed issupplied to the regulator 7. The regulator 7 controls the voltagefluctuation (data component) of the electric signal supplied from therectifier circuit 6, thereby stabilizing this electric signal. Thesignal thus stabilized is supplied, as DC power, to the sequencer 10.

The signal smoothed by the rectifier circuit 6 is supplied via themodulation circuit 12 to the HPF 8. The HPF 8 extracts thehigh-frequency component from the electric signal supplied from therectifier circuit 6. The high-frequency component is supplied to thedemodulation circuit 9. The demodulation circuit 9 demodulates thehigh-frequency signal input to it. The signal demodulated is supplied tothe sequencer 10. The sequencer 10 makes the RAM store the signal(command) input from the demodulation circuit 9. Using the programstored in the ROM, the sequencer 10 analyzes the signal. On the basis ofthe results of the analysis performed by the sequencer 10, the memory 11stores the data supplied from the demodulation circuit 9.

If the signal (command) input from the demodulation circuit 9 is a readinstruction, the sequencer 10 reads from the memory 11 the data thatcorresponds to this instruction. In accordance with the data read fromthe memory 11, the sequencer 10 performs switching on the FET 19 of themodulation circuit 12. When the FET 19 is turned on in the modulationcircuit 12, the loop coil 4 is connected to the impedance 18. When theFET 19 is turned off, the loop coil 4 is no longer connected in seriesto the impedance 18. Thus, the impedance of the loop antenna 54 of theR/W 50, which remains magnetically coupled with the loop antenna 2 ofthe IC card 1, changes in accordance with the read data. As a result,the terminal voltage of the loop antenna 54 varies with this impedance.The demodulation circuit 53 demodulates this variation of the terminalvoltage, whereby the R/W 50 can receive the read data.

Thus, communication is accomplished between the IC card 1 and the R/W50. Namely, the R/W 50 can write data into, and read data from, the ICcard 1, though it does not contact the IC card 1 at all.

The loop antenna 2 provided on the IC card 1 is an antenna apparatus 60so constituted as shown in FIGS. 3, 4 and 5. The antenna apparatus 60comprises a loop coil 61 and a magnetic member 62. The loop coil 61 isproduced by winding a conductive wire in a plane and configured toperform the inductive coupling. The magnetic member 62 covers one region61 a of the loop coil 61, from one surface F1 of the loop coil 61. Themagnetic member 62 passes through the loop coil 61 and covers the otherregion 61 b of the loop coil 61, from the other surface F2 of the loopcoil 61. That is, the loop coil 61 is covered by the magnetic member 62from one surface F1 and also from the other surface F2, thus the entireregion of the loop coil 61 is covered, at both surfaces.

The loop coil 61 has been formed by etching foils of conductive metal,such as electrolyte copper, provided on both surfaces of a flexibleinsulating film or substrate made of, for example, polyimide, PET or thelike. The method of forming the loop coil 61 is not limited to this. Theloop coil 61 may be formed by printing conductor patterns made ofconductive paste such as silver paste, or by sputtering a metal targetand thereby forming conductor patterns on the substrate. The regions 61a and 61 b of the loop coil 61 cover regions 61 d and 61 e that areopposed to the conductive wire that forms a rectangular coil. The loopcoil 61 has an insertion hole 61 c, through which magnetic member 62 isinserted and held. The insertion hole 61 c is circular or elliptical,having three or more apexes. The turns of the loop coil, which lie atone side, may be arranged at intervals different from those at theopposite side. In this case, the loop coil is an asymmetrical one,further increasing the communicable range.

The magnetic member 62 has a first part 62 a, a second part 62 b and aninsertion part 62 c. The first part 62 a covers the first region 61 a ofthe loop coil 61, from one surface F1 thereof. The second part 62 bcovers the other region 61 b of the loop coil 61, from the other surfaceF2 thereof. The insertion part 62 c passes through the insertion hole 61c and connects the first and second parts 62 a and 62 b. That part ofthe surface F1, which is not covered with the magnetic member 62, servesas a communication region. Namely, the surface F1 is opposed to the R/W50 to achieve communication with the R/W 50.

The region 61 b of the loop coil 61, which is covered with the secondpart 62 b of the magnetic member 62, has a larger area than the region61 a of the loop coil 61, which is covered with the first part 62 a ofthe magnetic member 62. The exposed part of the other region 61 b of theloop coil 61, i.e., the part not covered with the second part 62 b ofthe magnetic member 62, that is the one surface F1 is used ascommunication region.

The magnetic member 62 is broader and longer than the loop coil 61. Thefirst part 62 a and the second part 62 b cover the surfaces F1 and F2,respectively, whereby the loop coil 61 is covered in its entirety, atboth surfaces.

The insertion part 62 c of the magnetic member 62 is narrower andshorter than the first and second parts 62 a and 62 b thereof. That is,the magnetic member 62 has notches in both lateral edges of theinsertion part 62 c. These notches define the first part 62 a, thesecond part 62 b and the insertion part 62 c. The length of the notchesmay appropriately be selected in accordance with the thickness of themagnetic member 62 and the size of the insertion hole 61 c of the loopcoil 61. The first and second parts 62 a and 62 b are formed but notlimited by cutting notches. The first and second parts 62 a and 62 b maybe prepared independently and may then be jointed at the opening part.If this is the case, the loop coil may have regions covered, at bothsurfaces, with the first and second parts of the magnetic member 62.

To manufacture the magnetic member 62, a magnetic paint is prepared, bymixing a binder made of rubber-based resin, with magnetic powder, asolvent and an additive. Hie magnetic powder is made of Fe-basedmaterial that contains 96 wt % of Fe, 3 wt % of Cr, 0.3 wt % of Co andsome other magnetic materials. The magnetic paint is filtered, removing,from the binder, any magnetic particles having diameters larger than apredetermined value. In an extrusion molding machine, the magnetic paintis extruded from a tank through a nip between a pair of rollers, therebyforming a long magnetic: strip. The magnetic strip is dried, removingthe solvent therefrom.

Then, in a coating machine, one major surface of the magnetic strip iscoated with adhesive while the strip passes through the nip between apair of rollers. Further, the magnetic strip is punch-pressed, forming amagnetic member 62.

The magnetic member 62 can be made of any soft magnetic material andproduced by any method, so long as it exhibits satisfactory magneticcharacteristics. The magnetic material may be, for example, amorphousalloy, Co—Cr alloy, Fe—Al alloy, Sendust alloy (Fe—Al—Si), Fe—Ni alloy,Fe—Co—Ni alloy or the like. Powder of such an alloy is kneaded with arubber-based binder and dispersed in the binder, providing a paste. Thepaste is applied, forming the magnetic member. Alternatively, themagnetic member may be a thin soft magnetic plate formed byelectroplating or sputtering. Still alternatively, the magnetic membermay be a thin bulk plate made of only one material such as ferrite-basedpowder (Ni—Zn ferrite or Mn—Zn ferrite), press-sintered and containingno binder. Moreover, an insulating layer may be formed on the plate madeof the above-mentioned powder. To provide the insulating layer, an oxidefilm may be formed by heating and then be annealed, or an oxide film maybe formed by sputtering on the plate made of the powder. The magneticmember may be a sheet that has flexibility. Otherwise, it may be a hardplate made of sintered material, such as a ferrite plate.

The magnetic material 62 has, in its in-plane direction, an effectivemagnetic permeability μ′ (real-number part) of 30 or more and aneffective magnetic permeability μ″ (imaginary-number part) of 1.0 orless, each at the communication frequency. Since the magnetic material62 has effective magnetic permeability μ′ of 30 or more and effectivemagnetic permeability μ″ of 1.0 or less in the antenna apparatus 60, therange of communication between the IC card 1 and the R/W 50 can beexpanded even if the thickness of the magnetic material is reduced. Ifthe effective magnetic permeability μ′ is 50 or more, the communicationdistance can be increased.

To manufacture the antenna apparatus 60, an IC chip 63 is connected tothe loop coil 61 that has been produced as described above. As a result,the IC chip 63 and the coil 61 constitute a resonance circuit. The ICchip 63 used is, for example, an IC chip that accords with ISO 14443Standard or ISO 15693 Standard. The IC chip 63 is connected to the loopcoil by ACF method or wire bonding. Nonetheless, the method ofconnecting the IC chip is not limited in particular. Next, an insertionhole 61 c is made at the center part of the loop coil 61, so that themagnetic member 62 may pass through the loop coil 61. The insertion part62 c of the magnetic member 62 is inserted in the insertion hole 61 c.The first part 62 a covers the first region 61 a of the loop coil 61 atone surface F1, and the second part 62 b covers the other region 61 b ofthe loop coil 61 at the other surface F2. In this condition, the loopcoil 61 and the magnetic member 62 are bonded to each other. At thistime, the magnetic member 62 is so positioned that the adhesive-coatedsurface faces the major surface that is opposed to the loop coil 61. Theantenna apparatus 60 can thus be manufactured. Since the loop coil 61and the magnetic member 62 are bonded to each other with adhesive, withthe member 62 inserted in the insertion hole 61 c, the antenna apparatus60 can be easily manufactured in view of its structure. In addition,antenna apparatus 60 can be thin and small because the thickness of boththe magnetic member 62 and the loop coil 61 can be reduced.

A magnetic field is distributed at the antenna apparatus 60 thusconfigured, as is illustrated in FIG. 4. That is, the magnetic field isintense at one surface F1 of the loop coil 61, which is opposite to theother region 61 b that is covered with the second part 62 b of themagnetic member 62, which has a larger area than the first part 61 a.That is, the distribution of the magnetic field at the antenna apparatus60 is asymmetrical, unlike the symmetrical distribution of the magneticfield that the conventional antenna apparatus generates. Moreover, theintensity of the magnetic field can be adjusted by changing the areas ofthe regions that the first and second parts 62 a and 62 b cover,respectively.

Hence, the antenna apparatus 60 can increase the communication distancebetween the IC card 1 and the R/W 50 by controlling the distribution ofthe magnetic field radiated from the loop coil 61 and can widen thecommunicable range. The antenna apparatus 60 can enable the IC card 1and the R/W 50 to communicate with each other. That is, the R/W 50 canwrite data into, and read data from, the IC card 1, without contactingthe IC card 1.

In the antenna apparatus 60 according to the embodiment of thisinvention, the

magnetic member 62 is arranged as shown in FIG. 4, covering the firstregion 61 a of the loop coil 61 at one surface F1, and passes throughthe loop coil 61, covering the other region 61 b and at the othersurface of the loop coil 61. Thus, the magnetic member 62 covers allregions of the loop coil 61, at one surface and the other surface,whereby the magnetic field distribution at one surface F1 of the loopcoil 61 can be emphasized. The antenna apparatus 60 can therefore bemade thin and small. Further, since the intensity of the magnetic fieldis increased, the range of the communication between the IC card 1 andthe R/W 50 can be expanded.

In the antenna apparatus 60 according to the embodiment of the presentinvention, the magnetic field distribution at one surface F1 of the loopcoil 61 is emphasized and the magnetic member used has a predeterminedeffective magnetic permeability μ′ and a predetermined effectivemagnetic permeability μ″. Therefore, the antenna apparatus can be thinand can expand the communication range, greatly increasing thecommunication distance in a free space. In addition, the influence ofany metal member can be reduced, greatly increasing the communicationrange in the metal member.

As described above, the antenna apparatus 60 according to this inventionimproves the readiness of the communication between the IC card 1 andthe R/W 50 and enables the R/W 50 to write data into, and read datafrom, the IC card 1, reliably without contacting the IC card 1.

The loop antenna 2 provided on the IC card 1 may be such an antennaapparatus 70 as shown in FIG. 6. This antenna apparatus 70 isasymmetrical, because the opposing sides of the loop coil differ interms of the width of windings and/or the intervals thereof.

As FIG. 6 shows, the antenna apparatus 70 comprises a loop coil 71 and amagnetic member 72. The loop coil 71 is produced by winding a conductivewire in a plane and configured to perform the inductive coupling. Themagnetic member 72 covers one region 71 a of the loop coil 71, from onesurface of the loop coil 71. It passes through the loop coil 71 andcovers the other region 71 b of the loop coil 71, from the other surfaceof the loop coil 71. That is, the loop coil 71 is covered with themagnetic member 72 at all regions from both surfaces. The loop coil 71has been manufactured in the same way as the loop coil 61 describedabove. The loop coil 71 is formed asymmetrical in terms of the widths ofwindings at the opposing sides. Namely, the part 71 e covered with theregion 71 b of the loop coil 71 has a greater winding width than thepart 71 d covered with the region 71 a. Further, the loop coil 71 has aninsertion hole 71 c, through which magnetic member 72 is inserted andheld. Tire insertion hole 71 c is circular or elliptical, having threeor more apexes.

The magnetic member 72 has a first part 72 a, a second part 72 b and aninsertion part 72 c. The first part 72 a covers the one region 71 a ofthe loop coil 71, from one surface thereof. The second part 72 b coversthe other region 71 b of the loop coil 71, from the other surfacethereof. The insertion part 72 c passes through the insertion hole 71 cformed in the loop coil and connects the first and second pails 72 a and72 b. That part of one surface, which is not covered with the magneticmember 72, serves as communication region. Thus, this surface of theloop coil 71 is opposed to the R/W 50.

The region 71 b of the loop coil 71, which is covered with the secondpart 72 b of the magnetic member 72, has a larger area than the region71 a of the loop coil 71, which is covered with the first part 72 a ofthe magnetic member 72. The part 71 e at which the loop coil 71 has alarge winding width is arranged in the other region 71 b that is coveredwith the second part 72 b having a large area. The exposed part of theother region 71 b of the loop coil 71, i.e., the part not covered withthe second part 72 b of the magnetic member 72, which has a large area,is used as communication region.

The magnetic member 72 is broader and longer man tire loop coil 71. Thefirst part 72 a and the second part 72 b cover one surface and the othersurface, respectively, whereby the loop coil 72 is covered in itsentirety, at both surfaces.

The insertion part 72 c of the magnetic member 72 is narrower than thefirst and second parts 72 a and 72 b thereof. That is, the magneticmember 72 has notches in both lateral edges of the insertion part 72 c.These notches define the first part 72 a, the second part 72 b and theinsertion part 72 c. The length of the notches may appropriately bedetermined by the thickness of the magnetic member 72 and the size ofthe insertion hole 71 c of the loop coil 71. The first and second parts72 a and 72 b are formed but not limited by cutting notches. The firstand second parts 72 a and 72 b may be prepared independently and maythen be jointed at the opening part. If this is the case, the loop coilmay have regions that are covered, at both surfaces, with the first andsecond parts of the magnetic member. This magnetic member 72 ismanufactured in the same way as the above-described magnetic member 62.Therefore, how it is made will not be explained in detail.

To manufacture the antenna apparatus 70 according to the presentinvention, an IC chip 73 is connected to the loop coil 71 produced asdescribed above. As a result, the IC chip 73 and the coil 71 constitutea resonance circuit. The IC chip 73 is the same as the IC chip 63described above, and the method of connecting the chip 73 is the same asthe method of connecting the chip 63. Further, the method of bonding themagnetic member 72 to the loop coil 71 is the same as in manufacturingthe antenna apparatus 60 described above.

The magnetic field distribution at the antenna apparatus 70 thusconfigured is emphasized at one surface that is opposed to that surfaceof the other region 71 b covered with the second part 72 b having alarge area from the regions of the loop coil 71 which is covered withthe first and second parts 72 a and 72 b of the magnetic member 72. Thisis because the second parts 72 b having a large area is covered and alsobecause the winding width of the other part 71 e of the loop coil 71,which is arranged in the other region 71 b covered with the second part72 b, is broader than the part 71 d. Here, the winding width of the part71 e of the loop coil 71 arranged in the other region 71 b covered withthe second part 72 b is broader than the part 71 d. Nevertheless, thesame advantage can be attained even if the turns of the winding at thepart 71 e are arranged at longer intervals than at the part 71 d.

That is, the distribution of the magnetic field at the antenna apparatus70 is asymmetrical, unlike the symmetrical distribution of the magneticfield that the conventional antenna apparatus generates. Moreover, theintensity of the magnetic field can be adjusted by changing the areas ofthe regions that the first and second parts 62 a and 62 b cover,respectively, and by changing the intervals and/or width of the rums ofthe winding at the other part 71 e of the loop coil 71, which arearranged in the other region 71 b that is covered with the second part72 b.

Therefore, this antenna apparatus 70 can increase the communicationdistance between the IC card 1 and the R/W 50 by controlling thedistribution of the magnetic field radiated from the loop coil 71 andcan widen the communicable range. The antenna apparatus 70 can enablethe IC card 1 and the R/W 50 to communicate with each other. That is,the R/W 50 can write data into, and read data from, the IC card 1,without contacting the IC card 1.

In the antenna apparatus 70 according to the present invention, themagnetic member 72 is arranged, covering one region 71 a of the loopcoil 71 at one surface, and passes through the loop coil 71, coveringthe other region 71 b at the other surface. Thus, the magnetic member 72covers all regions of the loop coil 71, at one surface and the othersurface. In addition, the winding width of the pail 71 e of the loopcoil 71 arranged in the other region covered at the other surface isbroader than the part 71 d. Hence, only the magnetic field distributionat one surface of the loop coil 71 can be emphasized. The antennaapparatus 70 can therefore be made thin and small. Moreover, the antennaapparatus 70 can expand the range of the communication between the ICcard 1 and the R/W 50, because the intensity of the magnetic field isincreased.

In the antenna apparatus 70 according to the present invention, themagnetic field distribution at one surface F1 of the loop coil 71 isemphasized and the magnetic member used has a predetermined effectivemagnetic permeability μ′ and a predetermined effective magneticpermeability μ″. Therefore, the antenna apparatus can be thin and canexpand the communication range, greatly increasing the communicationdistance in a free space. Furthermore, the influence of any metal membercan be reduced, greatly increasing the communication range in the metalmember.

As described above, the antenna apparatus 70 according to this inventionimproves the readiness of the communication between the IC card 1 andthe R/W 50 and enables the R/W 50 to write data into, and read datafrom, the IC card 1, reliably without contacting the IC card 1.

Embodiments of the antenna apparatus 60 according to the presentinvention will be described below. More precisely, four comparativeexamples of the antenna apparatus 60 according to this invention will bedescribed with reference to FIG. 7 to FIG. 14.

Antenna apparatus 110, i.e., comparative example 1, comprises a loopcoil 111 and a magnetic member 112 as shown in FIG. 7 and FIG. 8. Theloop coil 111 is produced by winding a conductive wire in a plane andconfigured to perform the inductive coupling. The magnetic member 112 isbonded to the surface of the loop coil 111, which faces away from thesurface that may face an IC card 1. The magnetic member 112 is broaderand longer than the loop coil 111.

Antenna apparatus 120, i.e., comparative example 2, comprises a loopcoil 121 and a magnetic member 122 as shown in FIG. 9 and FIG. 10. Theloop coil 121 is produced by winding a conductive wire in a plane andconfigured to perform the inductive coupling. The magnetic member 122 isbonded to the surface of the loop coil 121, which faces away from thesurface that may face an IC card 1. The magnetic member 122 is narrowerand shorter than the loop coil 121.

Antenna apparatus 130, i.e., comparative example 3, comprises a loopcoil 131 and a magnetic member 132 as shown in FIG. 11 and FIG. 12. Theloop coil 131 is produced by winding a conductive wire in a plane andconfigured to perform the inductive coupling. The magnetic member 132 isbonded to the loop coil 131, such that it passes through the insertionhole of the loop coil 131 and is bonded, covering a part of the coil 131at one surface and covering another part of the coil 131 at the othersurface. The magnetic member 132 is narrower and longer than the loopcoil 131.

Antenna apparatus 140, i.e., comparative example 4, comprises a loopcoil 141 and a magnetic member 142 as shown in FIG. 13 and FIG. 14. Theloop coil 141 is produced by winding a conductive wire in a plane. Themagnetic member 142 is bonded to the loop coil 141, such that it passesthrough the insertion hole of the loop coil 141 and is bonded, coveringa pail of the coil 141 at one surface and covering another part of thecoil 141 at the other surface. The magnetic member 142 is narrower andshorter than the loop coil 141.

Assume that embodiments 1 and 2 of the same structure as the antennaapparatus 60 according to this invention and the antenna apparatuses110, 120, 130 and 140, i.e., comparative examples 1 to 4, each have sucheffective magnetic permeabilities μ′ and μ″ as shown in the followingTable 1. These antenna apparatuses were evaluated for the communicationdistances they achieve. Table 1 shows the communicable distance in ametal member and the communicable distance in a free space, which eachapparatus achieved. Note that embodiment 1 and comparative example 1have a magnetic member made of ferrite-based magnetic material and thatembodiment 2 and comparative example 2 have a magnetic member made ofFe—Si—Cr-based magnetic material. The effective magnetic permeability μ′is the AC specific permeability measured at the earner frequency (13.56MHz) by an impedance analyzer or the like, for ring-shaped samples, eachcomprising a ring having a diameter (φ) of, for example, 7 mm and a5-turn wire coil wound around the ring.

TABLE 1 Example Example Comparative Comparative Comparative Comparative1 2 Example 1 Example 2 Example 3 Example 4 Structure Antenna AntennaAntenna Antenna Antenna apparatus apparatus apparatus apparatusapparatus 60 110 120 130 140 Frequency [MHz] 13.56 13.56 13.56 13.5613.56 13.56 at the measuring point Effective magnetic 30 40 30 30 30 30permeability μ′ (real-number part) Effective magnetic 0.4 0.1 0.4 0.40.4 0.4 permeability μ″ (imaginary-number part) Result 30 mm 35 mm 20 mm15 mm 22 mm 20 mm (communicable distance in a metal member) Result 40 mm40 mm 40 mm 40 mm 40 mm 40 mm (communicable distance in a free space)

As seen from Table 1, embodiments 1 and 2, i.e., antenna apparatuses 60according to the invention, can increase not only the communicabledistance in a free space, but also the communicable distance in a metalmember. That is, they can expand the communicable range.

Further, in the antenna apparatuses, i.e., embodiments 1 and 2, theeffective magnetic permeability μ′ and the effective magneticpermeability μ″, both measured at the communication frequency in thein-plane direction of the magnetic member, can be 30 or more and 1.0 orless, respectively. Moreover, they can expand the range of communicationbetween the IC card 1 and the R/W 50.

Embodiments of the present invention have been described, with referenceto the drawings. Nonetheless, the invention is not limited to theembodiments. As is obvious to those skilled in the art, various changes,replacements and the like can be made, without departing from the scopeof the claims appended hereto.

1. An antenna apparatus for use in a non-contact type IC card into andfrom which data can be written and read by electronic apparatuses havinga communication function, by virtue of inductive coupling, the antennaapparatus comprising: a loop coil produced by winding a conductive wirein a plane and configured to perform the inductive coupling; and amagnetic member covering an undersurface of a first region of the loopcoil, passing through the loop coil, and covering a top surface of asecond region of the loop coil, wherein the undersurface of the loopcoil and the top surface of the loop coil are covered by the magneticmember.
 2. The antenna apparatus according to claim 1, wherein theundersurface of the loop coil is a region for communication with theelectronic apparatus, and the top surface at which the loop coil iscovered with the magnetic member has an area larger than that of theundersurface at which the loop coil is covered with the magnetic member.3. The antenna apparatus according to claim 1, wherein the undersurfaceof the loop coil is a region for communication with the electronicapparatus, and a winding which the loop coil has at the second region isbroader than a winding which the loop coil has at the first region. 4.The antenna apparatus according to claim 1, wherein the undersurface ofthe loop coil is a region for communication with the electronicapparatus, and winding turns which the loop coil has second region arearranged at longer intervals than winding turns which the loop coil hasat the first region.
 5. The antenna apparatus according to claim 1,wherein the magnetic member has a first part covering the undersurfaceof the loop coil, provided at the first region, from the undersurface, asecond part covering the second region of the loop coil, provided at thesecond region, from the top surface, and an insertion part passingthrough an insertion hole made in the loop coil and coupling the firstpart and the second part, and the undersurface of the loop coil, whichis not covered with the magnetic member, is a region for communicationwith the electronic apparatus.
 6. The antenna apparatus according toclaim 5, wherein the insertion part of the magnetic member is narrowerthan the first and second parts.
 7. The antenna apparatus according toclaim 6, wherein the first part and the second part are broader than theloop coil.
 8. The antenna apparatus according to claim 7, wherein theundersurface of the loop coil is a region for communication with theelectronic apparatus, and the top surface at which the loop coil iscovered with the magnetic member has an area larger than that of theundersurface at which the loop coil is covered with the magnetic member.9. The antenna apparatus according to claim 8, wherein the undersurfaceof the loop coil is a region for communication with the electronicapparatus, and a winding which the loop coil has at the second region isbroader than a winding which the loop coil has at the first region. 10.The antenna apparatus according to claim 8, wherein the undersurface ofthe loop coil is a region for communication with the electronicapparatus, and winding turns which the loop coil has at the secondregion are arranged at longer intervals than winding turns which theloop coil has at the first region.
 11. The antenna apparatus accordingto claim 5, wherein the first part and the second part are larger thanthe loop coil.